The present invention is based on a unipolar transverse flux machine.
In one known machine of this type (European Patent Disclosure EP 0 544 200 A1), where it is called a hybrid synchronous machine with transverse magnetic flux, the toothing of each rotor ring has one row of teeth extending over the outer circumference of the rotor ring, remote from the rotor axis, and one row of teeth extending on the inside circumference, toward the rotor axis, of the rotor ring, and the two rows of teeth have the same tooth pitch. The rows of teeth on each rotor ring are offset from one another by one tooth pitch. The yoke pitch on the stator corresponds to the tooth pitch of an inner or outer row of teeth, so that one outer tooth of one rotor ring and one inner tooth of the other rotor ring are always simultaneously located beneath one stator yoke. The two rotor modules, each comprising two rotor rings with axially unipolarly magnetized ring magnets located between them, are firmly fastened to the sides, remote from one another in the axial direction of the rotor, of a rotor body that is braced on the housing via rotary bearings. The stator yokes of each stator module that are received by the housing are embodied in the form of a U, and with their yoke legs oriented parallel to the rotor axis, they fit over the inner and outer rows of teeth of the two rotor rings of the rotor modules. The circular-annular coil, disposed concentrically to the rotor axis, in each stator module passes through the stator yokes at the base of the yoke, or in other words is located in the region between the annular face, pointing away from the rotor body, of the outer rotor ring and the crossbar of the stator yokes.
Transverse flux machines with permanent magnet excitation are known from the literature, such as the dissertation by Michael Bork, Entwicklung und Optimierung einer fertigungsgerechten Transversalfluxcex2maschine [Developing and Optimizing a Transverse Flux Machine to Meet Production Requirements], Dissertation 82, RWTH Aachen, Shaker Verlag Aachen, Germany, 1997, pages 8 ff. The circularly wound stator winding is surrounded by U-shaped soft iron yokes, which are disposed in the direction of rotation at the spacing of twice the pole pitch. The open ends of these U-shaped yokes are aimed at the air gap between the stator and rotor and form the poles of the stator. Facing them, permanent-magnet chips are disposed in such a way that the two chips that face the poles of a stator yoke have the opposite polarity. To short-circuit the permanent magnets, which in the rotor rotation are intermittently located between the poles of the stator and have no ferromagnetic short circuit, short-circuit elements are disposed in the stator. The short-circuit elements prevent the flux of the permanent magnets from being scattered along the yoke legs and the annular coil and prevent the effectiveness of the stator flux concatenation from being reduced by attenuation of the stator flux. Hence the short-circuit elements bring about a marked increase in the power of the machine.
The unipolar transverse flux machine of the invention has the advantage of simple modular construction, with which any desired number of lanes of the machine can be achieved by adding or deleting identically embodied stator and rotor units or in other words can be put together in modular fashion. As the number of module units, each composed of one stator module and one rotor module, increases, the concentricity of the machine improves, and an initially intermittent behavior of the machine changes over to continuous concentricity, without ripples in the course of the moment. Since the total moment of the machine is the sum of the moment components of the module units, the total moment of the machine can be adapted easily to existing requirements, without problems.
Compared to conventional transverse flux machines, the unipolar transverse flux machine of the invention has the advantage of a simple, unipolar magnetization of the rotor and of simple construction, by the avoidance of a great number of individual permanent magnets. The flux generated in the stator winding no longer passes primarily through the permanent magnets but instead through the teeth of the rotor rings, and it closes by way of the short-circuit elements, so that better utilization of the teeth is achieved. The result is better conditions for flux guidance, and the total amount of stray flux is reduced. In addition, the short-circuit elements serve to create an opposite pole in the stator, so that the same number of poles is obtained in both the stator and the rotor. The annular coil, whose outward-oriented portions between the stator yokes have a relatively large surface area, can be readily cooled, so that high current densities in the annular coil are attainable.
By means of the provisions recited in the other claims, advantageous refinements of and improvements to the unipolar transverse flux machine defined by claim 1 are possible.
In one advantageous embodiment of the invention, the short-circuit elements are in the form of a C, with two short legs each radially facing a rotor ring and with one crossbar, connecting the legs to one another, that extends parallel to the rotor axis on the inside, toward the rotor axis, of the annular coil, which is embodied circularly.
In an alternative embodiment of the invention, the short-circuit elements are embodied identically to the stator yokes and are in the form of a U, each with two long legs radially facing a rotor ring and with one crossbar connecting these long legs and extending parallel to the rotor axis. The annular coil of the stator module is shaped in meandering fashion, point-symmetrically to the rotor axis in the radial plane, in such a way that in successive alternation the annular coil extends through the space between the legs of a stator yoke and beyond the outside, remote from the rotor axis, of a crossbar of a short-circuit element. This has the advantage that the same tool can be used for both the yokes and the short-circuit elements, so that with the same tool, higher production can be achieved. The annular coil can be put into the meandering shape relatively simply.
In an advantageous embodiment of the invention, each stator module is received in a housing that comprises two half shells, which are embodied identically and placed on one another mirror-symmetrically and which have axially aligned radial grooves for insertion of the stator yokes and the short-circuit elements and also have indentations, for receiving the annular coil, that face one another mirror-symmetrically and are oriented concentrically to the housing axis. As a result, a self-supporting stator construction is achieved with identical components and simple joining technology, a construction that is maximally well suited to highly automated large-scale mass production. The self-supporting and self-locking function with exact positioning of the stator module elements (stator yokes, short-circuit elements, annular coil) is not limited to merely the individual stator module but instead is also used for positioning other stator modules relative to one another and for transmitting force and moment.
In a preferred embodiment of the invention, each half shell has a gridlike structure with an inner ring and an outer ring concentric to it. Both rings are integrally joined to one another by radial ribs. The radial grooves that receive the short-circuit elements are placed in the inner ring, while the radial grooves that receive the stator yokes extend across the inner ring, radial rib, and outer ring. This grid structure with openings located between the radial ribs makes an intensive heat transfer possible from the active magnetic and electrical stator elements to the cooling medium, which is air, and thus makes an intensive heat dissipation to the environment possible.
In an advantageous embodiment of the invention, the stator yokes and the radial grooves that receive them are adapted to one another such that when the stator yokes have been inserted into the radial grooves, the two half shells are fixed against one another radially and axially nondisplaceably. Thus the stator yokes have two functions, first that of magnetic flux guidance and second that of a mechanical clamp, which holds and correctly positions the half shell.
To achieve the mechanical clamp function, in an advantageous embodiment of the invention, the stator yokes, on both sides of their crossbar, each have a respective protruding hook, which when the stator yokes have been inserted into the radial grooves fits by positive engagement over one radial rib of the two half shells, on its back side remote from the radial groove.
In a multi-lane version of the unipolar transverse flux machine, in which the rotor modules are disposed in axial alignment on the rotor shaft and the stator modules are rotated from one another by a fixed angle, which with a two-lane embodiment amounts to 90xc2x0 electrically and for an m-lane embodiment amounts to 360xc2x0/m electrically, where m greater than 2, two spaced-apart radial recesses are made, from the outsides of the half shell that are remote from the radial grooves, in the annular portions of the outer ring, extending in the radial ribs, of the half shells, and the width of these radial recesses is equivalent in the circumferential direction to the width of the protruding hooks, while their radial depth is equivalent to the axial depth of the roots of the protruding hooks. For mirror-symmetrical placement of the two identical half shells on one another, the radial recess is disposed in the annular portion offset by the fixed angle from the following radial groove for a stator yoke, while the other radial recess is offset by the same fixed angle from the preceding radial groove for a stator yoke. The protruding hooks of the adjacent stator module protrude into one of these radial recesses per annular portion, and assure the requisite rotational angle offset between adjacent stator modules.
In an alternative embodiment of the multi-lane version, the stator modules are axially aligned, while the rotor modules are rotated from one another on the rotor shaft by the same fixed angle as defined above. In such an embodiment of the multi-lane machine, the above-described radial recesses in the outer ring are omitted, and the stator yokes of the stator modules located side by side in the axial direction are joined together in their crossbar region by axially extending bridges. On their outer side, the two outer stator yokes, of the joined-together stator yokes each have one hook protruding from the crossbar, which hook, when the stator yokes have been inserted into the radial grooves, fits over a radial rib of the two outer half shells on its back side remote from the radial groove. The stator yokes joined together, with the bridges located between them, are preferably embodied as one-piece stamped parts.